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S. Machida, Y. Gotoh, M. Kaneko, Y. Toba, A. Ohtaki, D. Kurosaka; Comparison of the Photopic Negative Response Obtained Under Different Recording Conditions in Glaucomatous Eyes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):215.
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© ARVO (1962-2015); The Authors (2016-present)
The aim of this study was to compare clinical significance of the photopic negative response (PhNR) recorded under different stimulus conditions in glaucomatous eyes.
Ten eyes of 10 normal volunteers and 80 eyes of 50 patients with open angle glaucoma (OAG) were examined in this study. The photopic electroretinogram (ERG) was elicited by white stimuli (1000 cd/m2) under a white background (40 cd/m2) (designated as W/W) or red stimuli (640 nm, 1600 cd/m2) under a blue background (470 nm, 40 cd/m2) (designated as R/B). Mean deviation (MD) and pattern standard deviation (PSD) were obtained by static visual field analysis. The topography of the optic nerve head was evaluated by confocal scanning laser ophthalmoscopy. The retinal nerve fiber layer thickness (RNFLT) around the optic nerve head was measured using scanning laser polarimetry.
The i-wave elicited by W/W was larger than that by R/B; it obscured a trough of the PhNR. In glaucomatous eyes, the PhNR amplitudes recorded under the two different conditions were highly correlated with each other (R=0.79, P<0.0001). Reduction of the PhNR amplitude was associated with loss of MD (R=0.46 and P=0.0007 for W/W; R=0.53 and P<0.0001 for R/B). A negative correlation was found between the PhNR amplitude and PSD (R=-0.41 and P=0.003 for both W/W and R/B). The PhNR amplitude was correlated with the rim area of the optic nerve head (R=0.29 and P=0.03 for W/W; R=0.38 and P=0.007 for R/B). A significant correlation was found between the PhNR amplitude and cup/disc area ratio only when R/B was used (R=-0.37, P=0.008). RNFLT was correlated with the PhNR amplitude (R=0.32 and P=0.02 for W/W; R=0.39 and P=0.005 for R/B). Although the correlation coefficients obtained under R/B were generally higher that those under W/W, this difference was not significant.
The PhNR amplitude elicited by either stimulus condition reflects functional and morphological loss of retinal ganglion cells in OAG. Although no significant difference was found, R/B may be more a suitable stimulus for recording the PhNR than W/W in OAG.
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